1. Field of the Invention
The present invention relates generally to internal combustion engines, and more particularly to a rotary internal combustion engine having a group of rotors that define a working volume.
2. Description of the Background Art
While the reciprocating piston engine is by far the most commonly used form of internal combustion engine at present, those skilled in the art have long appreciated that there are several disadvantages associated with such piston engines. These disadvantages include the inefficiencies created by the reciprocating motion of the pistons within the cylinders. The typical crank and connecting rod arrangement used to couple pistons to the power output shaft create intermittent inertial loads which limit peak piston velocities. Further, mechanical friction results from piston thrust on cylinder walls due to the angle of the crank and connecting rod. Typical mechanical efficiencies of piston type engines are only 75%. In addition, piston engines have a relatively great number of components.
In addition, piston engines have limited valve port sizes, which limit how quickly combusted exhaust gases can be ejected and which limit how quickly a fresh combustible mixture can be charged within the working volume of the piston. These porting limitations also limit the size of the engine and the speed of rotation.
Others have proposed the use of pure rotary engines to eliminate the inefficiencies associated with linear reciprocating pistons. For example, in U.S. Pat. No. 710,756 to Colbourne, a rotary engine is disclosed including four rotary vanes which contact each other and which rotate synchronously about parallel shafts, each vane shaft being geared with a central gear on a main shaft. Some of the vanes have admission ports formed therein through which a pressurized working fluid is admitted into the interior space bounded by the rotors.
In U.S. Pat. No. 2,097,881 to Hopkins, a rotary engine is described including a grouping of four rotors each in frictional contact with two rotors adjacent thereto. Gears are used to synchronize the speed and angular position of each of the four rotors. The four rotors define an inner working chamber the volume of which increases and decreases as the rotors rotate. Grooves are formed in selected rotors for conveying combustible gases to and from the working volume.
Likewise, in U.S. Pat. No. 3,439,654 to Campbell, a positive displacement rotary internal combustion engine is described having four elliptical cam pistons which rotate synchronously and which form a combustion chamber between them. Each elliptical cam piston rotates on a shaft; each piston shaft is provided with a pinion gear that meshes with a drive gear on the main power output shaft. The main power shaft synchronizes each of the four piston shafts. The casing surrounding the pistons includes a series of intake ports, exhaust ports, and transfer ports to introduce a fuel mixture and scavenge exhaust gases.
U.S. Pat. No. 3,809,026 to Snyder describes a rotary vane internal combustion engine having groupings of four rotors, each of elliptical cross sectional outer configuration. The housing surrounding the rotors includes air inlet ports and exhaust gas outlet ports, and a fuel injection port communicates with each combustion chamber. The rotors are synchronized by gearing to rotate in unison. A blower is powered by the engine to blow fresh air into the air inlet ports. One of the rotors has slots formed therein for allowing fresh air into a working volume, and for allowing exhaust gases to escape from the working volume. The described engine has a diesel or compressive means of initiating combustion within the combustion chamber.
In French Patent No. 1.128.173 to Dalo, a device is shown wherein four elliptically-shaped rotors are shown, and wherein one of the four rotors has one end cut off to allow access to the working volume bounded by the four rotors.
None of the above-described patent disclosures are believed to take full advantage of the high speed that pure rotary engines potentially offer, and thereby achieving higher power. Applicants believe that the principal limitation on the speeds achievable by such prior art structures is due to the limited gas flow rates through such devices. In other words, such prior art devices do not permit fresh air to be induced quickly enough, nor permit exhaust gases to be exhausted quickly enough, to obtain high operating speeds. Moreover, many of such prior art devices rely on valve port holes formed in the casing surrounding the rotors, which port holes are sealed or opened as the rotor rotates past such port holes. However, porting of inlet and exhaust gases through casing sidewalls results in small port areas, high gas pressure loss, and low flow at high operating speeds.
Accordingly, it is an object of the present invention to provide a rotary internal combustion engine having a relatively small number of moving parts, and wherein moving parts undergo rotary motion only.
It is another object of the present invention to provide a rotary internal combustion engine of the type having rotors having walls which rotate past each other with a continuous, uniform running clearance to define a working volume therebetween, and wherein the engine can be operated at high speed to achieve greater power.
It is a further object of the present invention to provide such a rotary internal combustion engine wherein the volume surrounding the rotors can be used for both intake and exhaust flow functions at essentially atmospheric pressure.
It is a still further object of the present invention to provide such a rotary internal combustion engine wherein the porting of inlet and outlet gases does not rely on valve ports that are opened or sealed by passage of the rotor past an opening in the casing surrounding such rotors.
These and other objects of the present invention will become more apparent to those skilled in the art as the description of the present invention proceeds.